/**
  * Provides requestAnimationFrame in a cross browser way.
  * @author paulirish / http://paulirish.com/
  */
 
 if ( !window.requestAnimationFrame ) {
 
 	(function() {
 	    var lastTime = 0;
 	    var vendors = ['webkit', 'moz'];
 	    for(var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
 	        window.requestAnimationFrame = window[vendors[x]+'RequestAnimationFrame'];
 	        window.cancelAnimationFrame =
 	          window[vendors[x]+'CancelAnimationFrame'] || window[vendors[x]+'CancelRequestAnimationFrame'];
 	    }
 	
 	    if (!window.requestAnimationFrame)
 	        window.requestAnimationFrame = function(callback, element) {
 	            var currTime = new Date().getTime();
 	            var timeToCall = Math.max(0, 16 - (currTime - lastTime));
 	            var id = window.setTimeout(function() { callback(currTime + timeToCall); },
 	              timeToCall);
 	            lastTime = currTime + timeToCall;
 	            return id;
 	        };
 	
 	    if (!window.cancelAnimationFrame)
 	        window.cancelAnimationFrame = function(id) {
 	            clearTimeout(id);
 	        };
 	}());
 
 }